<!DOCTYPE html>
<style>
body { background-color: white; }
#outer
{
  width: 100px; height: 100px;
  padding: 1px;
  background-color: black;
}
#inner
{
  width: 100px; height:100px;
  background-color: white;
}
</style>
</head>
<body>
<div id="outer"><div id="inner"></div></div>
</body>
</html>